at the start of WWII the US didn't have an army to speak off and the investments in the army were just neglible because with the worst economic crisis behind them they were investing much more in social security, infrastructure and economic growth

they needed 2 tot three years to have something of an army and to have enough weapons and boats and places and so on which led to a total re-organisation of the army and of the industry

the US can not say today that she has no army and no weapons and that it's budget is so small that you can't do anything else than just sit by and Watch